How do we know if all our efforts are just in vain?

I’ve been scrolling through the platform today, seeing dozens of launches, upvotes, and celebrating teams. It’s inspiring. But it also made me think about the personal sacrifices behind these numbers. Behind every "Successful Launch" post, the sleepless nights, impacted personal lives, and that anxious feeling that your self-worth is entirely tied to your metrics.
How do we know if all our efforts will truly pay off?
How do we actually distinguish between genuine persistence and just over-committing to an unviable idea?